Bassett et

ABSTRACT

1. A METHOD OF GROUTING AN OFFSHORE STRUCTURE HAVING AT LEAST ONE SUPPORTING LEG INCLUDING A TUBULAR JACKET EXTENDING DOWNWARDLY FROM ABOVE THE WATERLINE TO THE SEABED AND A PILING DRIVEN THROUGH SAID JACKET INTO THE SEABED WITH AN ANNULAR SPACE EXISTING BETWEEN THE INSIDE OF THE JACKET AND SAID PILING, SAID METHOD COMPRISING THE STEPS OF A. SEALING THE UPPER END OF SAID JACKET TO SAID PILING SO AS TO CLOSE SAID ANNULAR SPACE AT THE UPPER END OF THE JACKET, B. INTRODUCING COMPRESSED AIR INTO SAID ANNULAR SPACE AT A POINT ADJACENT THE UPPER END OF THE JACKET AND ABOVE THE WATERLINE SO AS TO EXPEL WATER FROM SAID SPACE THROUGH THE LOWER END OF THE JACKET, C. INTRODUCING FLUID GROUTING MATERIAL INTO SAID ANNULAR SPACE AT A POINT ADJACENT THE UPPER END OF THE JACKET AND ABOVE THE WATERLINE AFTER WATER HAS BEEN EXPELLED FROM SAID SPACE AS AFORESAID, D. SIMULTANEOUSLY MAINTAINING STATIC AIR PRESSURE IN SAID ANNULAR SPACE SUFFICIENT TO PREVENT INGRESS OF WATER THROUGH THE LOWER END OF SAID JACKET WHILE THE GROUTING MATERIAL IS BEING INTRODUCED INTO SAID SPACE, AND E. PERMITTING THE GROUTING MATERIAL TO SET.

NOV- 5, 1914 BASSETT ET AL. Re. 28, 232

METHODS OF GROUTING OFZJmL- r :mucwhs Original Filed Sbpl- Lu, .259

United States Patent 28,232 METHODS OF GROUTING OFFSHORE STRUCTURES MaxBassett, Houston, Tex., and Horace W. Olsen, de-

ceased, late of Houston, Tex., by Magdalene M. Olsen, executrix,Houston, Tex., assignors to C. Nelson Shields, .lr., trustee OriginalNo. 3,601,999. dated Aug. 31, 1971, Ser. No. 858,951, Sept. 18, 1969.Application for reissue July 11, 1973, Ser. No. 378.196

Int. Cl. E02]; I7/00; E02d 5/24 US. Cl. 6l-46 Claims Matter enclosed inheavy brackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISCLOSURE A method for grouting the annulus between thejacket and piling in the legs of an offshore structure in which air isintroduced to expel water from the lower end of the annulus, and theannulus is then filled from the top with grouting material. Air pressuremay be maintained in the annulus sufficient to prevent ingress of waterthrough the lower end of the jacket while grouting material is beingintroduced.

[Compressed air is introduced into an annular space existing between thejacket and piling in the legs of an offshore structure so that water isexpelled from the annular space through the lower end of the jacket andgrouting material is then introduced into the annular space. Theintroduction of compressed air and grouting material is effected fromabove the waterline, thus avoiding the necessity of performing thegrouting operation by divers at the sea bed] This invention relates tonew and useful improvements in methods of grouting offshore structuresused in the oil and gas industry. Such structures usually havesupporting legs each conisting of a tubular jacket which extendsdownwardly from above the waterline to the seabed, and a piling which isdriven through the jacket into the seabed. Some clearance necessarilyexists, and this results in an annular space between the inside of thejacket and the piling, which space has to be filled with groutingmaterial, particularly in the region of the lower end of the jacket, inorder to attain rigidity sufiicient for withstanding tides, oceancurrents, and the like.

It has been common in the art for the grouting operation to be performedby divers working at the bottom of the structure on the seabed, andapart from the obvious difficulties inherently associated with workingunder water, the conventional method often failed to produce fullysatisfactory results because water could not be effectively excludedfrom the space which the grouting material was intended to fill and thegrouting material itself became diluted and difficult to set.

The principal object of the invention is to eliminate the above outlineddisadvantages of conventional grouting procedures, this being attainedby providing an improved grouting method which may be easily andconveniently practiced from above the waterline rather than by diversbelow, and which assures proper placement and setting of the groutingmaterial by exclusion of water therefrom.

With the foregoing more important object and features in view and suchoher objects and features which may become apparent as thisspecification proceeds, the invention will be understood from thefollowing description taken in conjunction with the accompanyingdrawings, wherein like characters of reference are used to designatelike parts, and wherein:

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FlG. l is an cleva'ional view showing a typical installation of anoffshore structure on the sea bed;

FIG. 2 is an enlarged, fragmentary vertical sectional view of one of thelegs of the structure, showing the method step of expelling water fromspace between the jacket and piling of the leg; and

FIG. 3 is a fragmentary sectional view. similar to the lower portion ofFIG. 2 and showing the grouting material in place.

Referring now to the accompanying drawings in detail, the generalreference numeral 10 in FIG. 1 designates a typical offshore structuresuch as is used in the oil and gas industry for offshore drilling. thestructure 10 as shown being only the base portion which is beinginstalled on the seabed 12, prior to providing the base portion with theusual deck and other superstructure (not shown). The structure 10includes a plurality of supporting legs, each in the form of a tubularjacket 13 which extends downwardly from above the waterline 14 to theseabed 12, the several leg jackets being secured together bycross-members l5 and diagonals 16 in the conventional manner.

Each leg also includes a tubular piling 17 which is driven through thejacket 13 into the seabed I2, and inasmuch as some clearance isnecessary, an annular space 18 comes into being between the inside ofthe jacket 13 and the piling 17, as shown in FIG. 2. This annular spacemust be filled with grouting material, particularly in the region of thelower end of the jacket 13. not only in order to attain leg rigiditysufiicicnt to withstand tides. ocean currents and the like, but also toprotect the piling and the inside of the jacket against corrosion by seawater and air.

After the piling 17 has been driven through the jacket 13 into theseabed 12, the piling is cut off at the upper end of the jacket and thetwo components are secured together, as by a Weld 19, prior toinstallation of the deck and other superstructure. The welding operationat 19 in effect constitutes the first step of the method of theinvention. in that it seals or closes off the annular space 18 at theupper end of the jacket 13.

The second step of the method involves the introduction of compressedair into the annular space 18, as for example through a compressed airline 20 which is equipped with a suitable control valve 21 and apressure gauge 22 and communicates with the annular space 18 at a pointadjacent the upper end of the jacket 13, abo\e the water line 14. Withthe introduction of compressed air. any water in the annular chamber 18is forced downwardly and outwardly through the lower end of the jacket13 in o the seabed 12, and when all water has been expelled from thespace 18, bubbles of air will rise through the seabed and through thewater above to the waterline 14, as indicated at 23, thus giving avisible indication that all water has been expelled from the space 18.

In the event that the seabed 12 is not sufficiently soft or muddy topermit the escape of Water and air from the annular space 18 as abovedescribed, a suitable vibrator device 25 may be attached to the upperend portion of the jacket 13 above the waterline 14, so as to vibratethe jacket 13 and break its bond with the relatively firm seabed,sufliciently to facilitate expulsion of water and air from the space 18as already explained.

In any event, when all the water has been expelled from the annularspace 18, the compressed air supply through the line 20 is controlled bythe valve 21 and monitored by the gauge 22 so as to produce a static airpressure in the space 18 sufficient to prevent ingress of sea waterthrough the lower end of the jacket 13. While this condition prevails,suitable grouting material is introduced into the annular space 18, asfor example from a hopper 26 through a conduit 27 under the action of apump 28, the

conduit 27 communicating with the annular space 18 at a point adjacentthe upper end of the jacket 13, above the waterline 14.

The grouting material thus fills the annular space 18 as indicated at 29in FIG. 3, and while grouting of the lower end portion of the space ismost important, the entire length of the space may be grouted to abovethe waterline. If the seabed 12 is soft and muddy, some of the groutingmaterial may flow out of the lower end of the jacket 13 as indicated at29. In such event this initial fill of grout may be permitted to set,before grouting the rest of the annular space 18. in any event, thegrouting material is constrained or loaded by the air pressure until itis fully set or changed from a fluid to a solid form. This prevents thegrouting material from shrinking and assures its tight bond to the wallsof the jacket and piling, so that no seepage of sea water can occur tocorrode and deteriorate the composite strength of the grouted unit.

It may be noted that although the invention is primarily concerned withgrouting of offshore structures of the type mentioned, the teachings ofthe invention are also applicable to grouting of similar structures ingeneral. that is, not necessarily those which rest on the seabed.

What is claimed as new is:

1. A method of grouting an olfshore structure having at least onesupporting leg including a tubular jacket extending downwardly fromabove the waterline to the seabed and a piling driven through saidjacket into the seabed with an annular space existing between the insideof the jacket and said piling; said method comprising the steps of a.sealing the upper end of said jacket to said piling so as to close saidannular space at the upper end of the jacket;

b. introducing compressed air into said annular space at a pointadjacent the upper end of the jacket and above the waterline so as toexpel Water from said space through the lower end of the jacket;

c. introducing fluid grouting material into said annular space at apoint adjacent the upper end of the jacket and above the waterline afterwater has been expelled from said space as aforesaid;

d. simultaneously maintaining static air pressure in said annular spacesufiicient to prevent ingress of water through the lower end of saidjacket while the grouting material is being introduced into said space;and

e. permitting the grouting material to set.

2. A method of grouting an ofishore structure having at least onesupporting leg including a tubular jacket extending downwardly fromabove the waterline to the seabed and a piling driven through saidjacket into the seabed with an annular space existing between the insideof the jacket and said piling; said method comprising the steps of a.sealing the upper end of said jacket to said piling so as to close saidannular space at the upper end of the jacket;

b. introducing compressed air into said annular space so as to expelwater from said space through the lower end of the jacket;

c. introducing fluid grouting material into said annular space at apoint adjacent the upper end of the jacket after water has been expelledfrom said space as aforesaid: and

d. permitting the grouting material to set.

3. A method as defined by claim 2 and including maintaining static airpressure in said annular space sulficient to prevent ingress of waterthrough the low er end of said jacket while the grouting material isbeing introduced into said space.

4. A method as defined by claim 2 wherein an initial fill of grant isallowed to set before grouting the rest of the annular space,

5. A method as defined by claim 3 wherein an initial fill of grout isallowed to set before grouting the rest of the annular space.

6. A method as defined by claim 2 wherein the air is introduced at apoint adjacent the upper end of the jacket.

7. A method of grouting an ofishore structure having at least onesupporting leg including a substantially vertically extending tubularjacket in the water and a piling in said jacket having an outsidediameter smaller than the inside diameter of the jacket whereby a spaceis formed between the inside of the jacket and said piling; said methodcomprising the steps of a. scalingly enclosing said space at its upperend;

b. introducing compressed gas into said space so as to expel water fromsaid space through the lower end of the jacket;

c. introducing fluid grouting material into said space at a pointadjacent its upper end after water has been expelled from said space asaforesaid; and

d. permitting the grouting material to set.

8. A method as defined by claim 7 wherein said tubular jacket extendsdownwardly at least to the seabed and said piling is driven into theseabed, whereby the lower end of said space is open to the seabed.

9. A method as defined by claim 7 and including maintaining static airpressure in said space suflicient to prevent ingress of water throughthe lower end of said jacket while the grouting material is beingintroduced into said space.

It). A method as defined by claim 8 wherein an initial fill of grout isallower to set before grouting the rest of the space.

IL A method as defined by claim 8 wherein the gas is introduced at apoint adjacent the upper end of the space.

12. A method of grouting an oflshorc structure having at least onesupporting leg including a substantially vertically extending tubularjacket having its lower end in the seabed and a piling in said jacketdriven into the seabed having an outside diameter smaller than theinside diametcr of the jacket whereby a space is formed between theinside of the jacket and said piling; said method comprising the stepsof a. sealingly enclosing said space at its upper end;

b. introducing compressed gas into said space so as to expel water fromsaid space through the lower end of the jacket into the seabed until allthe water has been expelled from said space;

6. controlling the gas pressure to maintain a static gas pressuresufficient to prevent ingress of sea water through the lower end of thejacket;

(I. introducing an initial fill of fluid grouting material into saidspace at a point adjacent its upper end while such gas pressure is beingmaintained;

e. permitting the initial fill of grouting material to set;

f. introducing sufficient additional grouting material to substantiallyfill said space; and

g. permitting the additional grouting material to set.

13. A method of grouting an ofishore structure having at least onesupporting leg including a substantially vertically extending tubularjacket in the water and a piling in said jacket having an outsidediameter smaller than the inside diameter of the jacket whereby a spacecontaining water is formed between the inside of the jacket and saidpiling; said method comprising the steps of a. sealingly enclosing saidspace at its upper end;

b. introducing compressed gas into said space so as to expel the waterfrom said space through the lower cud of the jacket;

c. introducing fluid grouting material into said space at a pointadjacent its upper end after substantially all of the water has beenexpelled from said space as aforesaid; and

d. permitting the grouting material to set.

14. A method as defined by claim 13 and including maintaining static airpressure in said space sufiicien! 6 to prevent ingress of water throughthe lower end of UNITED STATES PATENTS said jacket while the groutingmaterial is being in- 3,209,544 10/1965 Borrmann "odlwed said W3,492,s24 2/1970 Evans et a1. 61-46.5 15. A method as defined by claim14 wherein an initial 3 5 4 355 2 197 Bloum et a]. 1 45 fill of grout isallowed to set before grouting the rest of 5 3,597,930 8/1971 R h ll 6146 the space. 3,187,513 6/1965 Guild 6153.6 X

References Cited The following references, cited by the Examiner, areJACOB SHAPIRO Pnmary Exammer of record in the patented fi1e of thispatent or the original 10 patent. 61-5352, 53.6, 54

